Abstract
Widespread application of thermoelectric devices for waste heat recovery requires low-cost high-performance materials. The currently available n-type thermoelectric materials are limited either by their low efficiencies or by being based on expensive, scarce or toxic elements. Here we report a low-cost n-type material, Te-doped Mg3Sb1.5Bi0.5, that exhibits a very high figure of merit zT ranging from 0.56 to 1.65 at 300−725 K. Using combined theoretical prediction and experimental validation, we show that the high thermoelectric performance originates from the significantly enhanced power factor because of the multi-valley band behaviour dominated by a unique near-edge conduction band with a sixfold valley degeneracy. This makes Te-doped Mg3Sb1.5Bi0.5 a promising candidate for the low- and intermediate-temperature thermoelectric applications.
Highlights
Widespread application of thermoelectric devices for waste heat recovery requires low-cost high-performance materials
We show that the exceptionally high thermoelectric performance originates from a considerably enhanced power factor that is aided by the combination of a low resistivity and an enhanced Seebeck coefficient contributed by the multiple band behaviour dominated by a unique near-edge conduction band with a high valley degeneracy of 6
We find that the Seebeck coefficient and power factor of n-type doping are much better than those of p-type doping for binary Mg3Sb2
Summary
Widespread application of thermoelectric devices for waste heat recovery requires low-cost high-performance materials. High n-type performance at 300 À 725 K shown in Mg3Sb1.48Bi0.48 Te0.04 is comparable to the best current state-of-the-art n-type materials[5,12,23,24,25,26] such as Bi2Te3 À xSex and AgPbmSbTe2 þ m (Fig. 1b) that, contain a large amount of expensive, scarce or toxic heavy elements such as Te, Ag and Pb. Combining theory and experiment, we show that the exceptionally high thermoelectric performance originates from a considerably enhanced power factor that is aided by the combination of a low resistivity and an enhanced Seebeck coefficient contributed by the multiple band behaviour dominated by a unique near-edge conduction band with a high valley degeneracy of 6
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